Conventional fixing devices include one having a fixing roller, a pressure roller, and an electromagnetic induction heating section (see JP 2001-135470 A). The electromagnetic induction heating section performs induction heating of the fixing roller. The fixing roller and the pressure roller fix images on paper sheets through application of heat and pressure.
The electromagnetic induction heating section has an annular exciting coil and a degaussing coil which cancels magnetic flux of the exciting coil. The inside diameter of the annular exciting coil is larger than a paper feed area for large-size paper sheets.
However, in the conventional fixing device, the inside diameter of the annular exciting coil was larger than the paper feed area for the large-size paper sheets, which caused a problem that a non-paper feed area on the fixing roller for the large-size paper sheets was heated. Moreover, since the exciting coil was large, it was impossible to achieve downsizing and cost reduction of the electromagnetic induction heating section.
Further, the presence of the degaussing coil brought about further upsizing of the electromagnetic induction heating section and thereby caused a problem of cost increase in the electromagnetic induction heating section.